Slime preventative compositions and methods



Sept. 23, 1958 z v.'MoUDRY ET AL 2,853,449

SLIME PREVENTATIVE COMPOSITIONS AND METHODS Filed sept. 2, 1955 2 sheets-sheet 1 INVENTORS ZDE/VEK V. MOUDRy, Mik/E M Moya/Py,

lm, W

swswvaswo svga/4 /v/ 044740.91 Masaya ATTORNEYS z. v. MOUDRY ET AL sept. 23, 1958 l 2,853,449

I SLIME PREVENTATIVE COMPOSITIONS AND METHODS y 2 Sheets-Sheet 2 Filed Sept. 2^, 1955 ATrORNEY SLIME PREVENTATIVE COMPOSITIONS AND METHODS Moudry and Marie K. Moudry,

Northfield, Ill.,

application september z, V195s, serial' No. 532,306 7 claims. (ci. 21o-64) Y .Zdenek Vaclav l phenylmercuric acetate has been used'withvarying degrecs of success in the treatment of recirculating kwaters to control slime in paper mills and' liker installations. However, slime preventatives based on phenylmercuric acetate have not been entirely satisfactory. The primary disadvantage has been that the slime preventing capabilities of phenylmercuric acetate alone are not really adequate for many purposes. Diiculty also arises from the fact that phenylmercuric acetate is so sparingly ysoluble in water and other media involved' that it is often not'practical to uniformly distribute through the'medium being treated a quantity of phenylmercuric acetate'` ade quate to inhibit the growth of slime producing organisms. For example, in treating paper mill white water, it is .possible to dissolve adequate phenylmercuric acetate' by adding it in the beaters, but it is not practical to add phenylmercurio acetate at other pointshin the system where the water is moving rapidly. Yet, in many'cases, suclinas plants manufacturing newsprint, the 'slime V 'controlling agent-should be added fat such other vvpoints', trather"thar1 in the beaters. The present invention is based upon the discovery that solutions of phenylmercuric acetate containing relatively small proportions of "'rrietallicf silver V rnicroparticles""are unusually effective in preventing slime formation in aque"- ousl and other liquidmedia.- Thus, it has been found'th'at phenylmercuric acetate solutions produced in 'accordance with` the present invention and containing a small amount of silver microparticles are as much as 10 times as effective, atpH 5, and lwell over 100 times'as eifective, at pH 8, in controlling slime producing korganisms in paper'rnill white water, as are vconventional solubilizedv phenylmercurio acetate preparations. Thus,'for example, a'concentration of 10 parts per million of acomposition, made in accordance with the present invention, 'in paper'mill white water at' pH 8 is 100 times aseifective as a concentration of 25 parts per million Eof solubilized phenylmercuric acetate in the same white water.

In general, compositions of they prevent invention-comprise solutions of 5'-12.5 parts byweight phenylmercuric acetate -in 85-62.5 parts by weight'of liquid organicfsolvent, with 0.3-1.0 part, by weightof metallic silver micrck Patented Sept'. 23,1958

ICC

particles uniformly distributedlthroughout theA solution; The solvents employed are the water soluble glycols-and thelower alkyl ethers thereof, e. g. :k

Ethylene glycol Diethylene glycol Triethylene glycol Propylene glycol v Dipropyleneglycol Hexylene glycol. Ethylene glycol monoethyl ether.-r vi Diethylene glycol monoethylether 2-methoxymethyl-2,4dimethyl pentanedioly-Yl,5r-hexane- The silver microparticles 'are advantageously predominantly vsm'all'er'than 700 A. U., and best results are obtained when the silverparticles are smaller'tha'n'v2r001ll Colloidal dispersions of such 'fine' silverparticles'cn be prepared by reducing silver nitrate in"an aqueous s'ol tion containing` a special gelatin. The gelatinv should have a-gel strength of l25-250, a viscosity of y20.--40niilli, poises in 62/a% aqueous solution; at 60 C., a pH of.3 .5

in .aqueous solution, an isoelectric point of pH 7.8-8.3, andan ash analysis 'not exceeding 2%, the ash beingfsubf stantially all calcium. The gelatinvmust be' substantially completely free from sulfur and ionizable halogen.

4Such a gelatin can be produced b'yacid hydrolysisof acid treated fresh-frozen pork skins. During hydrolysis, the characteristics above referred to change progressively, and the special gelatin is withdrawn as a selected fraction when 'these characteristics have attained the proper values. A. product of thisy type is Knox Gelatin`#84l, produced by Charles B. Knox Gelatine Co., Johnstown, N. Y;

Preparations of 'aqueous colloidal suspensions of silver microparticles suitable for use in the inventionis trated by the following example n AThe gelatin employed was Knox #841, having a gel strength of 165, a viscosity of 30 millipoises, a pH of 4.44, an Visoelectric point of pH 8, and an ash analysis of 1.2%, substantiallyall' the "ash being calcium. Thesilver nitrate was dissolved in Ya portion ofV the -water,"`a1 suspension of the gelatin in thev remaining wj'ater'was prepared, andthe silver nitrate solution and gelatin suspension were ,then combined, The resulting mixturewas then irradiated for `l5 seconds with actinic light at an intensity lof about.pl,062 milliwatts per square foot, at least.40% lof.the.total radiation being in lthe infrared portion of the spectrum and at least 25% in the ultraviolet portion, the. ultraviolet por. tion of theradiationfincluding a material proportion of light emitted 'at 3130 A. U. and 3660 AI U. The result-v ing product-was a stable aqueous dispersion ofsilver microparticles having a median maximum dimension'of A. U. Silverparticles smaller than 700A. U. constituted yabout 3.1% by weight of the total composition.v In'consideringthis percentage, vit should be noted5that water amounting to about 5% by weight of the composition is lost during irradiation. v .Inj preparing compositionsin accordance withthe Ypres-r entinvention, asolution of phenylmercuric acetatel the `solvent is iirst `prepared and an aqueous colloidal suspension of silver microparticles such as the suspension of Example I is then added. It is essential, particularly when working with large volumes, that the suspension of silver microparticles be added gradually with continual agitation, else the protein content of the suspension is denatured and the silver tends to precipitate. Further, it is necessary that the silver suspension be added after, rather than before, the phenylmercuric acetate has been dissolved, else 30-50% less phenylmercuric acetate can be dissolved. The ltemperature of the `solution must not exiceed about ,30 C. at the time the silver dispersion is added, else nitration of the nphenylmercuric radical and the hydroxyl groups of the solvent will occur. Such `nitration is noticeable if the temperature is increased `to 35 C. In order that a uniform distribution ofthe silver microparticles in the phenylmercuric acetate solution may be maintained, the aqueous suspension of silver microparticles employed should contain 0.1-5 by weight of the gelatin, so that the gelatin amounts to U01-1.5% by weight of the nal composition.

The following example illustrates the improved compositions of the present invention, and the method for preparing them:

Example Il Percent by weight Phenylmercuric acetate 8.3 Composition of Example I 17 ,0 D iethylene glycol `monoethyl ether 74.7

The diethylene glycol monoethyl ether at room temperature was placed in a motorized laboratory scale mixer and an excess of phenylmercuric acetate was added. Agitation was then continued for 30 minutes and the solution filtered (the filtrate consisted of parts phenylmercuric acetate and 90 parts solvent, the necessary ex- ,cess of the phenylmercuric acetate to cause 10 parts to dissolve having been rst determined by trial).

yWith the resulting solution still at room temperature,

the l`7 parts of aqueous colloidal silver suspension obwherein the procedure is the same as for Example II:

Parts by Weight Example Example III IV Phenylmercuric acetate 5 12. 5 Composition of Example I. l0 25. 0 Glycol or Glycol Ether Solvent 85 62. 5

Since the composition of Example I contains about 3.1% by weight silver microparticles, the parts by weight of silver microparticles in Examples III and IV are about 0.31 and0.78, respectively. The silver microparticle content can be decreased to about 0.3, or increased to about l1.0 part by weight. The glycol or glycol ether solvent should not be reduced below the proportion indicated in Example IV, else it is not possible to incorporate the colloidal silver dispersion in the lsolution ofv phenylmercuric acetate without precipitating substantial quantities of' gelatin and silver.

The graph of Fig. l indicates the effectiveness of the composition of Example II in destroying slime producing organisms in paper mill white waters at pH 4-8 as compared with aV conventional composition containing solubilized phenylmercuric acetate without silver micro- .4 particles. The conventional composition consists of aqueous solution of sodium hydroxide-solubilized phenylmercuric acetate also containing sodium salts of orthophenylphenol. The tests were carried out by adding various quantities of the two compositions to samples of the white waters containing from 105 to 5 1O6 organisms per cc. and allowing the treated samples to stand for a 4-hour exposure period, after which the number of viable organisms was then determined. It will be noted that, at all pH values between 4 and 8, one part per million of the composition of Example II destroyed in excess of of the slime producing organisms, while about 10 parts per million of the solubilized phenylmercuric acetate composition were required -to o-btain'this result at about pH 5.5, and over lparts per million of that composition were required to destroy 90% of the organisms at pH 8. As seen from Fig. l, the compositions are not only generally more eiective than conventional phenylmercurio acetate compositions, but are also unusually effective inthe higher VpH range.

Fig. 2 includes toxicity curves for equivalent amounts of the composition of Example Il, phenylmercuric acetate alone, silver microparticles alone, silver nitrate alone, and a solution of both phenylmercuric acetate and silver nitrate in diethylene glycol. The test samples were again white water samples from paper mills and the exposure period was again 4 hours in all cases. In these tests, the phenyl mercuric acetate was not solubilized, and the silver microparticles were prepared as in Example I. The curves of Fig. 2 are of particular' interest because they demonstrate that the effectiveness of the composition of Example Il is markedly greater than the total of the independent effects of phenylmercuric acetate and silver microparticles. Even under conditions most favorable to phenylmercuric acetate, the independent effects of phenylmercuric acetate and silver microparticles total at most about 60% of the effectiveness of the composition of Example II at concentrations on the order of 1 5 parts per million. It is also pertinent to note from Fig. 2 that, while silver nitrate alone has a microbicidal eiIect approaching that of oligodynamic silver, a solution of both silver nitrate and phenylmercuric acetate is found to be little more effective than silver microparticles alone.

A11 of the solvents hereinbefore recited give compositions in accordance with the invention which are readily miscible with aqueous media to be treated, and the solvents are Vgenerally interchangeable. Some of the water soluble glycols and their lower alkyl ethers are more effective as solvents for phenylmercuric acetate than are others. Thus, while the diethylene glycol monoethyl ether of Example Il is effective to provide a 10% solution of phenylmercuric acetate, a 14% solution may readily be prepared with ethylene Lglycol monoethyl ether as the solvent.

Example V An excess of phenylmercuric acetate was mixed with ethylene glycol monoethyl ether to form a solution containing 14 parts by weight phenylmercuric acetate Iand 86 parts by weight of the solvent. The excess phenylmercuric acetate was then ltered out and 83 parts by weight of the solution placed at room temperature in a motorized bowl mixer. To this solution was then added 17 parts by weight of the composition prepared in Example I, the `addition being carried out over a period of 15 minutes with continual agitation. The resulting composition, containing 11.6% by weight. phenylmercuric acetate, 71.4% by weight ethylene yglycol monoethyl ether and 17% by weight of the composition of Example I, exhibited all of the characteristics of the composition described in Example II. The silver microparticle content was again approximately 0.53l by weight.

It will be understood that the solvents referred to can be used in combination, rather than singly, without departing vfrom the scope of the invention.

We have also discovered that the activity of compositions in accordance with this invention may be further enhanced by including, in addition to silver, oligodynamic copper. `in such cases, the copper constitutes 0.01-0.3 part by weight of the composition, with silver remaining at 0.3-1.0 part by weight, based on a phenylmercuric acetate content of 5-12.5 parts by weight. The oligodynamic silver and copper may be prepared by simultaneously reducing a water soluble silver salt and a water soluble cupric salt, as disclosed in copending application Ser. No. 343,705, led March 20, 1953, by Zdenek V. Moudry. The following example is illustrative:

Example VI The procedure of Example I was repeated without change, except that 1.5 parts by weight cupric nitrate was dissolved along with the silver nitrate. Up-on irradiation, both the silver and copper salts were reduced, yielding a dispersion containing slightly more than 3% by weight oligodynamic silver and about .4% by weight oligodynamic copper. Spectrometric analysis indicated that the silver and lcopper were predominantly in physically combined form, though a material proportion of individual copper and silver microparticles was present. The particle size of substantially all of the oligodynamic metal was smaller than 700 A. U. with the greater portion being smaller than 200 A. U.

A nal composition was then prepared by dissolving 8.3 g. phenylmercuric acetate in 74.7 g. diethylene glycol monoethyl ether, following the procedure of Example Il, and then adding 17.0 g. of the silver-copper dispersion. The resulting composition contains approximately 0.5 g. oligodynamic silver and 0.08 g. oligodynamic copper.

Compositions prepared in accordance with the present invention are useful in controlling fungi, including M ucar spinosus, M ucor racemous, Cladosporum herbarum, Penicillium spinulosum, Pencillium cyclopium, Penicillum martensi, Aspergillus niger and Fusarium moniliforme, and bacteria, including Pseudomonas, B. subtilis, B. megatherium, iron bacteria including the genera Cladothrix, Leptothrix, Crenothrix, Aerobacter aerogenes and other members of the coliform group.

While the compositions of the invention are highly advantageous for use in any situation where slime-producing organisms are to be controlled in liquid media, they provide an especially effective solution to the problem of slime control in recirculating waters. In the case of recirculating waters, where there is usually not only a fairly large volume of liquid involved but also a large amount of apparatus surface area in -contact with the liquid, it is essential that the active ingredients of the slime inhibiting composition be uniformly distributed through the liquid and that such uniform distribution be maintained during use. Compositions of the present invention are simply added to the recirculating water and uniform distribution is accomplished and maintained by recirculation of the liquid. This is a result which has been difficult to attain with phenylmercuric acetate alone, or even with the socalled solubilized phenylmercuric acetate compositions.

What is claimed is:

1. A composition for inhibiting formation of slimes in liquid media comprising a solution of 5-12.5 parts by weight phenylmercuric acetate in 85-62.5 parts by weight of a solvent selected from the group consisting of the water soluble glycols and lower alkyl ethers thereof, said solution also containing uniformly distributed therethrough 0.3-1.0 part by weight of metallic: silver particles predominantly smaller than 700 A. U.

2. A Icomposition for inhibiting formation of slimes in liquid media comprising a solution of 5-12.5% by weight phenylmercuric acetate in -62.5 by weight of a solvent selected from the group consisting of the water soluble glycols and lower alkyl ethers thereof and, uniformly dispersed in said solution, an aqueous colloidal suspension of metallic silver particles, said suspension comprising 10-25% by weight of the total composition and containing silver particles smaller than about 700 A. U. amounting to v 0.3-1.0% by weight of the total composition.

3. A composition for inhibiting the growth of slimeproducing organisms comprising a solution of phenylmercurio acetate having uniformly distributed therethrough 0.3-1.0% by weight of metallic silver particles smaller than about 700 A. U.

4. A method for producing a slime inhibiting compositions comprising dissolving 5-12.5 parts by weight phenylmercurio acetate in 85-62.5 parts by weight ofa solvent selected from the group consisting of the water soluble glycols and the lower alkyl ethers thereof and then combining with such solution, with continual -agitation and at a temperature not exceeding about 30 C., 10-25 parts by weight of an aqueous colloidal suspension of metallic silver microparticles produced by reducing silver nitrate in an aqueous solution containing, a substantial proportion of an ioniazble-halogen-free, sulfur-free gelatin having a viscosity of 20-40 millipoises, an isoelectric point of pH 7.8-8.3 and a pH of 3-5.5, said aqueous dispersion persion containing metallic silver particles amounting to 0.3-1.0 part by weight of the total composition.

5. A composition for inhibiting formation of slimes in liquid media comprising a solution of 5-12.5 parts by weight phenylmercuric acetate in 85-62.5 parts by weight of a solvent selected from the `group consisting'of the water soluble glycols and the lower alkyl ethers thereof, said solution also having uniformly distributed therethrough 0.3-1.0 part by weight silver and 0.01-0.3 part by weight copper, the silver and copper being in microparticulate form.

6. A method for inhibiting the formation of slimes in recirculating waters comprising uniformly combining with such waters an effective proportion of a liquid composition comprising 0.3-1.0 part by weight of metallic silver microparticles uniformly distributedl in a solution of 5-12.5 parts by weight phenylmercuric acetate.

7. A method for inhibiting the formation of slimes in recirculating waters comprising incorporating in such waters an effective proportion of a liquid composition comprising 0.3-1.0 part by weight of metallic silver particles predominantly smaller than 700 A. U. uniformly distributed in a solution of 5-12.5 parts by weight phenylmercuric acetate in 85-62.5 parts by weight of a solvent selected from the group consisting of the water soluble glycols and lower alkyl ethers thereof.

References Cited in the le of this patent UNITED STATES PATENTS 1,460,012 Berend June 26, 1923 2,132,886 Voelker Oct. 11, 1938 2,183,493 Rentschler et al. Dec. 12, 1939 FOREIGN PATENTS 432,101 Great Britain July 15, 1935 OTHER REFERENCES Yagi: Rev. Phys. Chem. Japan, vol. 14, pp. to`127 (1940); through Chem. Abstracts, volume 35, page 4264. 

4. A METHOD FOR PRODUCING A SLIME INHIBITING COMPOSITIONS COMPRISING DISSOLVING 5-12.5 PARTS BY WEIGHT PHENYLMERCURIC ACETATE IN 85-62.5 PARTS BY WEIGHT OF A SOLVENT SELECTED FROM THE GROUP CONSISTING OF THE WATER SOLUBLE GLYCOLS AND THE LOWER ALKYL ETHERS THEREOF AND THEN COMBINING WITH SUCH SOLUTION, WITH CONTINUAL AGITATION AND AT A TEMPERATURE NOT EXCEEDING ABOUT 30*C., 10-25 PARTS BY WEIGHT OF AN AQUEOUS COLLOIDAL SUSPENSION OF METALLIC SILVER MICROPARTICLES PRODUCED BY REDUCING SILVER NITRATE IN AN AQUEOUS SOLUTION CONTAINING, A SUBSTANTIAL PROPORTION OF AN IONIAZABLE-HALOGEN-FREE, SULFUR-FREE GELATIN HAVING A VISCOSITY OF 20-40 MILLIPOISES, AN ISOELECTRIC POINT OF PH 7.8-8.3 AND A PH OF 3-5.5, SAID AQUEOUS DISPERSION PERSION CONTAINING METALLIC SILVER PARTICLES AMOUNTING TO 0.3-1.0 PART BY WEIGHT OF THE TOTAL COMPOSITION. 